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CNC Table saw

Aug 13th, 2019 | by: Jason Meech
Category: Electronics Basic Circuits
Views 279
So this project started as finding a use for some old SBR20 rails that are in rough shape, not quite worthy of a real CNC machine, but still pretty good. Also i want a table saw but am cheap. 



Goals:
  •  Table saw fence with digital read out
  •  Self positioning via steppers, 
  •  Position tracking for when fence is moved manually. 
  •  always on micro-controller via battery management system, cold tolerant (so machine doesnt need to home every time its turned on, position can be tracked when only the micro / encoder is powered, Like the way a digital caliper works) 

Stretch Goals:
  • DXF Support for uploading cut sheets and simply selecting the cut and having fence move to position
  • Blade memory so you can save the 0 position of the fence depending on the blade you're using 
  • CNC blade height and angle adjustment


Current Hardware (subject to change as i find stuff that works or doesnt) 
Transmission / Motion:
  • 2x SBR20 Rails 1240mm 
  • 2x Lead screws (forget part number its 1610 or something like that) 
  • Arduino mega + ramps board + drv8825 stepper drivers 
  • 2x nema 23 steppers (its what i had spare, could easily use smaller steppers) 
Electronics: 
  • Arduino Mega or UNO (see conundrums below) 
  • RPI zero-w 
  • Battery Management system (requires cold tolerance so probably not lithium) 


Status
 CAD for the main assembly is and prototyping with 3d printed parts has begun. 

Currently working on circuit design and sourcing what electronic components to use (aka looking thruogh my junk pile for stuff i can cut off) 


Conundrums: 
here is where im undecided...

Should i use something like an arduino uno or mega with some standard gcode loving firmware on it (grbl or marlin for example), then simply use an rpi to send gcode via usb... but do all the interactions with the RPI ie upload .dxf via wifi, have a touchscreen display etc.. 

OR 

Just have the RPI control the steppers directly via gpio (idk if that will work apparently the python library has poop for timing but idk how much that matters if its never under any load and doesnt have to move super fast) 


Normally i tend to do my projects very privately, and don't welcome or want outside help (it's my quiet time : ) and almost never post anything until its completed and tested to my satisfaction, but i've recently joined the modern world and have finally decided to participate in social media and human interaction in general. TL;DR i would welcome any input or assistance if anyone is interested :) 



External link to fusion360 web viewer for file: 

PHOTO GALLERY

Posting parts as they are 'finalized' (aka it at least seems to fit and i havent found any reason YET to redesign it : )



Rail assembly with
Fence assembly (designed for 25.4mm square tube)
LCD / Button panel layout

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